This invention relates to hand-held electric lamps, and in particular to hand-held inspection lamps with external electrical power supply.
As used herein, the term inspection lamp encompasses general illumination lamps and lamps with various color filters to emit light in selected ranges of wavelength, including infrared, visible and ultraviolet. The particular lamps described in this specification are filtered to emit in the ultraviolet and/or blue ranges to cause a flourescent response from flourescent tracer dyes for leak detection, coating and surface flaw inspection, and UV curing.
Inspection lamps requiring external electrical power supply are usually designed to connect exclusively to an alternating current (AC) or to a direct current (DC) power source, but not interchangeably to either AC or DC. Inspection lamps designed to connect to a DC source are typically smaller light-weight portable with a power cord having alligator clips for connecting to battery terminal posts or a plug for an automobile lighter socket. The AC lamps are typically larger and heavier, and have a power cord terminating in a three-prong grounded plug for use with an AC line voltage outlet.
The invention is directed to inspection or curing lamps which can be quickly configured to connect to either an AC outlet or a DC power source merely by changing to the appropriate power cord. The pin connections between the cords and lamp are adapted to connect or to by-pass certain internal circuitry within the lamp.
One type of lamp, for example, may have an internal AC to DC power converter enabling it to supply direct current to the bulb, regardless of the source. Another type of lamp may have an internal DC to AC converter to supply line voltage AC to the lamp, or to a transformer or impedance ballast to produce a particular voltage, frequency or waveform for lamp operation. Either type of lamp, in accordance with this invention, will have at least two detachable power cords with a multi-pin connection to the lamp. The pin connector circuitry in the lamp will remain unchanged by the power cord selection, but the pin connector circuitry in the power cords vary in how they connect certain pin sockets to the power source.
Typically, a power cord for AC line voltage has a three-prong grounded outlet plug. A power cord for DC typically has battery clips or a cigarette lighter plug. In this invention, a multi-pin plug at the opposite end of the power cord has the same number and configuration of pins in both the AC and DC cords, but the pin connections in the cord differs between the AC cord and the DC cords.
Using this invention in a lamp where a tungsten-halogen incandescent bulb is intended to be powered by 12-volt direct current, for example, the pin connections in the AC power cord automatically route the AC line current to an AC to DC power converter within the lamp, while the pin connections in the DC cords automatically by-pass the converter. Conversely, using the invention in a lamp where a high intensity discharge (HID) bulb is intended to be powered by high-voltage high-frequency alternating current, the pin connections in the DC power cords automatically route the DC current to a DC to AC power converter within the lamp, while the pin connections in the AC cords would automatically by-pass the converter and route the AC line current directly to a transformer/ballast device.
Various internal circuitry and pin configurations can be used, depending in part upon whether a particular polarity is required. Several alternative configurations are described herein.
In addition, there may be other novel features of the particular lamps described. The lamp with an AC-powered MDL light source has several safety features in its configuration.